To achieve small-sized large-capacity multilayer ceramic capacitors, dielectric layers have been thinned and the number of stacked dielectric layers has been increased to develop reliable products. As the dielectric layer becomes thinner, a stress due to the difference in contraction percentage between a dielectric layer and an internal electrode layer may generate a crack in the dielectric layer. The design of dielectric layers that determine the characteristics of the multilayer ceramic capacitor is important.
Disclosed is a technique that diffuses Ni into 3 to 30% of the distance between internal electrodes to improve the temperature characteristic of the capacitance (see Japanese Patent Application Publication No. 10-4027, hereinafter referred to as Patent Document 1, for example). Also disclosed is a technique that reduces insulation deterioration under high temperature and high voltage by arranging a composition region that homogeneously contains Mg or Ni as a dielectric layer so as to make contact with an internal electrode layer and making the central portion of the dielectric layer include a crystal grain in which neither Mg or Ni exists (for example, see Japanese Patent Application Publication No. 2010-232248 hereinafter referred to as Patent Document 2).
However, in the techniques of Patent Documents 1 and 2, Ni is not diffused in the middle portion of the dielectric layer in the stacking direction. In this case, the stress between the dielectric layer and the internal electrode layer is not sufficiently reduced. Therefore, it is difficult to solve the problem that a crack is generated in the dielectric layer.